This invention relates to a tooth assembly for ground engaging implements, and more particularly to a tooth assembly having a replaceable tip mountable onto an adapter.
Many ground engaging implements, such as excavator buckets and the like have a plurality of teeth (or more commonly teeth assemblies) mounted across the base or cutting edge of the bucket to increase the bucket""s penetration into the ground. Each tooth assembly includes a replaceable tip, which is mounted onto an adapter. The adapters are typically secured to the bucket""s base edge by welding and, therefore, are not readily replaceable. The tips, on the other hand, are typically detachably mounted to the adapter in manner so as to make them easily replaceable, as such tips wear out relatively quickly. Most tips are generally wedge shaped with a sharp leading edge when new, which gives them good penetration ability. However, as the tip wears, it can become increasingly blunt, making penetration difficult and digging less efficient. Also, tips and adapters are sometimes exposed to extremely large loads during use, such as when the bucket teeth are used to penetrate rock or to pry out large stones or boulders in the ground. Such extremely large loads can overstress either the tip or adapter. The adapter, while stronger, is susceptible to breaking because the load is applied to the adapter through a longer moment arm than on the tip. Adapter breakage is less desirable that tip breakage because the adapter is more expensive and its replacement is more time consuming. As a consequence, various methods have been employed in the past to aid in the transfer of loads from the tip to the adapter. One such method is disclosed in U.S. Pat. No. 5,386,653 issued Feb. 7, 1995 to Erwin D. Cornelius and assigned to the assignee hereof, wherein the tip is equipped with a pair of opposed ears that are received into slots in the sides of the adapter. Vertical loads are transferred from the tip through the top and bottom edges of the ears, which contact the upper and lower sides of the slots. Tips, however, are exposed to high lateral loads, as well as vertical loads. Due to cocking of the tip, the distal ends of the ears may contact the side surface of the slots in the adapter, whereby such high lateral loads may overstress the ears in a lateral direction, causing them to break as well.
The present invention is directed to overcoming one or more of the problems as set forth above.
In one aspect of the present invention, a tooth assembly is provided for a ground engaging implement. The tooth assembly includes an adapter and a replaceable tip. The adapter is carried upon the implement and has a predetermined vertical design load capacity sufficient to withstand a predetermined large vertical load without failing. The adapter also has a forwardly extending tip mounting nose portion. The replaceable tip has an elongated body with a rearward end portion and a forward ground penetrating end portion. The rearward portion has a rearwardly opening socket cavity adapted to receive the mounting nose portion of the adapter and the forward ground penetrating end portion has a leading cutting edge at its distal end. The forward ground penetrating end portion transitions from the mounting end portion to the leading edge in a manner so as to provide a necked down portion adjacent the socket cavity of the rearward end portion. Such necked down portion has a reduced cross-section sufficient to cause the tip to fail at the necked down portion when the tip is subjected to a sufficiently large vertical load, such sufficiently large vertical load being smaller than the predetermined vertical design load capacity of the adapter so that the tip will break before the adapter.
In another aspect of the present invention, the adapter has an ear receiving pocket on each of a pair of opposite sides of the adapter. Each ear receiving pocket has a side surface therein. The rearward end portion of the tip has a pair of side ears extending rearwardly from the socket cavity, each ear being adapted for receipt within a respective one of the ear receiving pockets for transferring vertical loads from the ears into the adapter. Each ear has a distal end and an inner surface that is disposed alongside the side surface of its pocket and that extends from the socket cavity to the distal end. Each of the inner surfaces is disposed at a slight angle relative to the mating side surface of adapter ear receiving pocket so as to diverge away from the side surface of the ear pocket to alleviate lateral loads from being exerted on the distal ends of the ears through lateral contact with the adapter.
In still another aspect of the invention, the forward ground penetrating end portion of the tip transitions from the rearward end portion to the leading cutting edge wherein the tip body is constructed such that the cross-sectional area of the tip body does not substantially increase from front to rear so as to maintain tip sharpness as the tip wears.